One of conventional digital to analog (simply called "D/A" hereinafter) converters comprises a first D/A converting means for converting upper four bits of a eight bit digital signal to a first analog signal, a second D/A converting means for converting lower four bits of the eight bit digital signal to a second analog signal, an attenuator for attenuating the second analog signal by an attenuation factor of 1/2.sup.4, and an adder for adding the first analog signal and the second analog signal which is attenuated.
In operation, the eight bit digital signal is supplied to the first and second D/A converting means by the upper and lower four bits separately so that the first and second analog signals are produced depending upon the contents of the upper and lower four bits. The second analog signal is then attenuated in the attenuator by the attenuation factor of 1/2.sup.4. Thereafter, the first analog signal and attenuated second analog signal are added so that an analog signal corresponding in its value to the eight bit digital signal is produced.
In the conventional D/A converter, however, there is occured an error at the middle value "zero" (the origin 0 of the coordinate axes) of the analog signal or in the vicinity thereof in a case where,
(1) a full scale of the second D/A converting means does not conform to that of the first D/A converting means,
(2) there is resulted an error in the attenuated second analog signal due to the characteristic of the attenuator, and
(3) a bit which is supplied to the first D/A converting means includes an error.
For these reasons, outputs of analog data are deteriorated in their characteristic, when inputs of digital data are of a value nearly at the origin 0 of the coordinate axes because such Ln error as described above is produced. In such an occasion, the characteristics of S/N ratio or waveform distortion is deteriorated in reproducing audio signal based on a weak power of digital signals.